Active material particles for a lithium secondary battery
Active material particles are provided that exhibit performance suitable for increasing the output of a lithium secondary battery and little deterioration due to charge-discharge cycling. The active material particles provided by the present invention have a hollow structure having secondary particles including an aggregate of a plurality of primary particles of a lithium transition metal oxide, and a hollow portion formed inside the secondary particles, and through holes that penetrates to the hollow portion from the outside are formed in the secondary particles. BET specific surface area of the active material particles is 0.5 to 1.9 m 2 /g.
1. Active material particles for a lithium secondary battery, comprising
a plurality of secondary particles, each secondary particle being composed of an aggregate of a plurality of primary particles of a lithium transition metal oxide and a hollow portion formed inside the each secondary particle, wherein
the lithium transition metal oxide is a compound having a layered structure that contains nickel as a constituent element thereof,
the each secondary particle constitutes an outer shell of the active material particle,
the outer shell has through holes that penetrate the outer shell to the hollow portion from the outside, wherein the through holes connect the outside of each active material particle and the hollow portion thereof along a straight line that passes through the through holes, and wherein the average number of through holes is 1 to 10 per particle of the each secondary particle, and
BET specific surface area of the active material particles is from 0.5 to 1.9 m 2 /g.
2. The active material particles according to claim 1 , wherein the opening width of the through hole is on average 0.01 μm or more.
3. The active material particles according to claim 1 , wherein the average hardness of the active material particles, as obtained by measuring dynamic hardness under conditions of a loading speed of 0.5 mN/sec to 3 mN/sec using a flat diamond indenter having a diameter of 50 μm, is 0.5 MPa or more.
4. The active material particles according to claim 1 , wherein the average particle diameter of the secondary particles is 3 μm to 10 μm.
5. The active material particles according to claim 1 , wherein the primary particles that compose the secondary particles are sintered in the portion of the secondary particles that surrounds the hollow portion, with the exception of the portions having the through holes.
6. The active material particles according to claim 5 , wherein the outer shell contains substantially no gaps observable by SEM at the grain boundaries thereof.
7. The active material particles according to claim 1 , wherein the lithium transition metal oxide is a compound having a layered structure that contains nickel, cobalt and manganese as constituent elements.
8. The active material particles according to claim 1 , wherein the average number of through holes possessed by the secondary particles is 1 to 3 per particle of the active material particles.
9. The active material particles according to claim 1 , wherein the BET specific surface area of the active material particles is from 0.5 to 1.48 m 2 /g.
10. A lithium secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte solution, wherein
at least one of the positive electrode and the negative electrode is an electrode containing a hollow active material having the active material particles according to claim 1 .
11. The lithium secondary battery according to claim 10 , which is used as a driving power supply of a vehicle.
12. A vehicle comprising the battery according to claim 10 .